This Article explores a feature of the law of causation in torts that has received little analysis: what I call “self-proving causation.” This is a class of negligence cases in which there is no direct evidence of cause-in-fact. Rather, there is circumstantial evidence resting on the fact that the defendant was negligent. In most tort cases, evidence of negligence cannot serve as the basis, and certainly not as the sole basis, of an inference that this negligence caused the harm for which the plaintiff seeks damages. But in self-proving causation cases that is precisely what occurs. So the question is, what distinguishes self-proving causation from other proof of causation? The Article first examines what makes self-proving causation cases distinctive. It then turns to what has become in a short time the most salient and provocative self-proving causation case ever decided, Zuchowicz v. United States. In an opinion by Judge Calabresi, the court held that, because overdoses of prescription drugs often increase the risk of harm, the plaintiff had introduced legally sufficient evidence of causation by proving that the defendant had negligently provided the plaintiff an excessive dose of a particular drug. The Article peels off the layers of the opinion in that case by identifying and evaluating the key steps in the reasoning that leads to its conclusion. Finally, the Article explores the precedential significance of Zuchowicz and its application in some subsequent cases, and considers what this analysis can tell us about the requirements for application of self-proving causation generally.